Age-hardening process



Patented July -3, 1928.

' UNITED STATES PATENT OFFICE.

' REGINALD SCOTT DEAN, LA GRANGE, ILLINOIS, AND WILLIAM EWAB'I HUDSON, OF

' LOS ANGELES, CALIFORNIA, ASSIGNOBS TO WESTERN ELECTRIC COMPANY, INCOR- POBATED, OF NEW YOBK, N. Y., A CORPORATION 01 NEW YORK.

AGE-HARDENINQ PROCESS.

No Drawing. Application flied September 16, 1924, Serial No. 737,998. Renewed October 20, 1927.

This invention relates to age-hardened metallic alloys and processes of producing I 6 articles.

Articles made of age-hardened metallic alloys may be produced in two general ways: The article may be cast in finished form and then age-hardened; or the article may be 10 produced by a. working process applied to a billet of the alloy and age-hardened, during, or after the forming process has been completed. An article produced by simple cast-.

, ing and age-hardening is more brittle and possesses less tensile strength than a worked article. A worked article, on the contrary, although possessing greater strength and being less brittle, as a eneral rule, will anneal and soften at a considerably lower temperaturethan a simple cast allo'y.

The object of this invention is to produce age-hardened metalic' alloys which are less brittle than simple cast age-hardened alloys and whose softening temperature is higher than the softening temperature; of worked age-hardened alloys of the same constitution.

Another object of the invention is the production of storage batte so treated that the final heat treatment there of may be produced with a minimum period :of heating.

The process of age-hardeningnmet-allic alloys in practice comprises'the t ee steps of heating, quenching and aging the alloy, certain details being observed in each case, de-

pending principally u n the alloy used and the relative qualities esired in the alloy after age-hardening. The heating ste is employed for the purpose of forming t e alloy 4 into a solid solution, and should preferably be continued until such a condition exists.

According to the main features of this invention, instead of a single heating ste ,this step of the process is'repeated a lura ity of times, 'and intermediate successive heating operations desired work is performed upon the alloy. The result is that at each succes- '-'=sive heating step a solid solution is obtained more quickly, and finally it is possible to heat the alloy and obtain such a condition almost instantaneously. The alloy is quenched and aged after the final heating. It may grids andthe like I and the quick heating which is possible when solid solution forms quickly, reduces the crystal growth due to such heating. In order to produce an alloy of maximum hardness it is essential that no work be performed onthe alloy between the final quenching and aging steps. This practice is necessary since Working of the alloy between these quenching and aging steps would tend to reduce the size of the cr stalline structure, which accordingly would result in a reduction of the hardness.

Although the heating step may be repeated any required number of times it is usually suflicient to heat the alloy, to obtain a solid solution, (or to cause the maximum amount of solute mate-rial present to enter solution, where there is more than the carrier metal can hold), perform work upon the alloy, reheat quickly to the temperature reuired to produce a solid solutlon, quench t e alloy and age it.

The invention is particularl adaptable to the treating of age-hardenab e lead-alloys of the character described in our copending application, Serial No. 690,716, filed February 5, 1924, wherein are disclosedlead alloys containing tin, antimony, etc., and particularly lead-antimony alloysvcontaining about 2.25 per cent antimony. The' specific application of the invention to the production of age-hardened lead alloys will now be more fully explained. The process for producin age-hardened alloys, such as those referre to in our conding application mentioned above, is riefly to heat the alloy until a state of solid solution exists therein, quench the alloy while still in a state of solid solution to a lower temperature, thereby forming a super saturated solid solution, and then. age the alloy at a temperature below C. During the aging process the alloy gradually assumes a more stable state, or a state of equilibrium and the hardness thereof gradually 7 increases. In our copending application,

7 permit the maximum amount of solute mate-' rial to enter solid solution, and immediately be of particular advantage in the production of storage battery grids, Such as those de- Serial No. 690,719, filed February 5, 1924, a process for hardening lead-antimony articles upon which work has been performed is disclosed. The principal distinction between the hardenin method as applied to cast articles and wor ed articles is that the constit uents of worked alloys can be formed into a solid solution more uickly than the constituents of alloys whic are simply cast.

According tothe main features of the present invention as applied to lead-alloys, the alloy is first reduced to a solid solution, this treatment causing it to readily re-enter solution after the alloying constituent has separated out of the lead. The article to be produced is then formed from the alloy, raised quickly to the temperature which will quenched. The alloy is then aged in the usual manner as described in our copending plication, Serial No. '690,7l6, referred to a ve.

By the process constitutin this invention, the crystal growth due to t e final heatin is reduced to a minimum and the alloy, having been previously formed into a solid solution, reforms into a solid solution very quickly with a. minimum amount of heating. A process embodying this inver ition may scribed in our copending application, Serial 'No. 690,720, filed February 5, 1924. \Vhen employed for this purpose the details of the process may be as follows The allo is east mto the form of a billet and heate until a solid solution is obtained. It is then cooled at any convenient rate and when cooled is rolled into thin sheets. It is then again heated to the temperature of maximum solubility and quenched from that temperature; The storagebattery grid may then be stamped from the sheet, preferably before the sheet has had suflicient time to harden. been formed, itis ain raised to the temperature required to o tain solid solution and immediately quenched. Since the storage ,battery grid is a oomparatively'small article and, since its surface is large in proportion to its bulk, it can be heated to an elevated temperature practically instantaneously and on account of the previous treatment a solid solution is produced without the necessity of continued application of heat. The crystal growth due to the 'final heating is therefore reduced to a The term softening temperature as used in the specification an the appended claims is defined as the temperature at which the age-hardened alloy will begin to lose its hardness.

Althpugh the has igllieen described asapp g articularyto street 0 lead-a113 arid more specificall to tl i d gro duction of storage battery gri it is to be After the grid has 7 forming understood-that the invention is to be lim-:

ited, only by the scope of the appended claims.

What is claimed is: 4

1. The method of treating an age-hardenable lead allo which consists in raising said alloy a plura ity of times to the temperature at which the maximum amount of solute material present will enter solid solution, performing work thereon between successive heating steps, quenching said alloy and then agingsaid alloy.

2. The method of treating age-hardenable lead alloys, which consists in forming the constituents of the alloy into a solid solution, coolin the alloy, performing work upon the alloy, heating said alloy to reform the solid solution, thenquenching and aging the alloy.

3. The method of treating age-hardenable lead alloys, which consists in casting the alloy, heating the alloy to obtain a solid solution, coolin the alloy, performing work upon the a oy, reheating the alloy to the temperature at which the maximum amount g of solute material present will enter solid solution, then quenching and aging the alloy. 4. The method of treating a lead alloy, which consists in casting a billet of said alloy, heating said billet at the temperature atwhich the maximumamount of solute material; present will enter solid solution,

.cooling the billet, performing work thereon,

reheating said alloy to the temperature at which the maximum amount'of solute material present will enter solid solution, then quenching and aging said alloy.

5. The method of producing a btorage battery grid, which consists in casting a billet of "an age-hardenable lead alloy, heating said billet until the maximum amount of solute material present entersesolid solution, coolin said billet, fabricating a grid therefrom,

re eating the grid to thetenrperature necessary to produce solid solution, then quench-- ing and a said grid.

6. The me od of producing a storage battery grid, which consists in casting a billet of an age-hardenable lead alloy, heating said billet until the maximum amount ofsolute material in said alloy enters solid solution,

cooling said billet, rolling said billet to a fiat sheet, reheating said alloy in the resulting fiat sheet form until the maximum amount of solute material therein enterse grid.

thereof into a solid solution and cooling the alloy a plurality of times, performing work thereon between successive solid solution forming steps and cooling steps, and aging the alloy after the final cooling step.

9'. The method of treating an age-hardenable lead alloy, which "consists in forming the constituents thereof into a solid solution, cooling the alloy, performing work upon the alloy, again forming the constituents into a solid solution, quenching the alloy, and aging the alloy. 7

10. The method of producing age-hardenable alloys, which consists in alloying antimony with lead, forming the constituents of the alloy into a solid solution, cooling the alloy, performing work upon the alloy, againforming the constituents into a solid solution, then uenching and aging the allo I 11. The method of producing age-har' ened alloys, which conslsts in alloying about 2.25 per cent antimony with lead, formin the constituents of the alloy into a soli solution, cooling the alloy, performing work upon the alloy, again forming the constituents into a solid solution, then quenching and aging the alloy.

12. The method of producing a storage battery grid, which consists in casting a billet of anage-hardenable lead-antimony alloy,

heating said billet until the antimony present enters solid solution, cooling said billet,

fabricatin a grid therefrom, reheating the grid to t e temperature necessar to produce solid solution, then quenc ingand aging said grid.

13. The method of producing a storage battery grid, which consists in casting a billet of an age-hardenable lead-antimony alloycontaining about 2.25 Per cent antlmo ny, heating said billet unti the antimony present enters solid solution, cooling said billet, fabricating a grid therefrom, reheating the grid to the temperature necessary to produce solid solution, then quenching and aging said grid.

14. The method of producing a storage battery grid, which consists in casting a billet of an age-hardenable lead-antimony alloy, heating said billet until the antimony in said alloy enters solid solution, cooling said billet, rollin said billet to a fiat sheet,

reheating said a loy in the resulting flat sheet form until the antimony therein enters solid solution, quenching said sheet, stam ing a grid therefrom, reheating said grid to reform the solid solution, quenching said grid, and agin the rid.

In witness w ereo we hereunto subscribe our names this 29th dayof August, A.'D. 1924.

, REGINALD SCOTT'DEAN.

WILLIAM EWART HUDSON. 

